


The One Thing That I Know

by loonyBibliophile



Category: Agents of S.H.I.E.L.D. (TV)
Genre: F/M, Step-siblings, this is a step sibling au, yes - Freeform
Language: English
Status: Completed
Published: 2014-03-06
Updated: 2014-03-26
Packaged: 2018-01-14 18:11:40
Rating: Not Rated
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 8
Words: 14,875
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/1276033
Author URL: https://archiveofourown.org/users/loonyBibliophile/pseuds/loonyBibliophile
Summary: <blockquote class="userstuff">
              <p>When Simmons meets Fitz, she is knock kneed and he is terrified and they are both too smart for their own good. Several months and a broken ankle later, their parents finally formally meet and sparks fly. But what will happen if years later, sparks start to fly between a pair of awkward genius step-siblings?</p>
            </blockquote>





	1. As Circumstances Would Have It

**Author's Note:**

> I'm so sorry in advance if I fudge up anything British. I'm a Californian born and bred and I'm doing my best. I hope at least someone enjoys this sill story about our favorite geniuses being childhood friends and step siblings who fall in love.

Leopold Fitz and Jemma Simmons meet for the first time at the tender age of nine. Fitz had just moved to the small town on the Southern coast of England from a slightly larger town in Scotland. Simmons is the enthusiastic class representative, all smiles and white teeth and a knock kneed, clumsy gait; the byproduct of a growth spurt she hasn't grown into quite yet. As all nine year old boys are, Fitz is annoyed by the fact that she is taller than him, but mostly he's just glad someone is talking to him. She sticks her hand out to shake and her elbows are so pointy it looks like her skin must hurt. 

"I'm Jemma Simmons! You're Leopold right? It's my job to show the new kids around!" he makes a face.

"Leo. Leopold is my grandad's name and I hate it."

"Kay! Do you want me to show you around?" there is hope in her voice as she stares at him expectantly. Being nine years old in a class of twelve year olds doesn't win her many friends, and neither does her enthusiasm about any given subject or the eagerness with which she throws her hand in the air. "How old are you by the way? I'm nine but everyone here is older than me, I skipped three grades." she beams with pride at that, no shame on her face for her confidence in her skill, even then. 

"Oh!" he brightens noticeably. "I'm nine too! I wonder if they put us in the same class on purpose." he muses out loud, staring at the tiled floor.

"I bet they did. The headmaster's always telling me she wants me to have 'peers who challenge me' so she bumped a bunch of grades but it's still pretty easy."

They become fast friends after meeting, despite their differences. Jemma Simmons is loud and confident and unabashedly sure of herself and her smarts and her decisions. She is not afraid of her intelligence. Leo Fitz fades into the background a little more, preferring to go unnoticed, but after school lets out and it's just him and Jemma walking to the sandwich shop or one of their flats, he is just as loud and boisterous as her, telling her excitedly about the new watch his mum bought him to take apart and how he put it back together better than before.

They don't just talk about school or science or math or books either. It doesnt take long for Fitz to confide in Simmons that he and his mum moved there from Scotland because his parents got divorced and they'd needed to move in with his aunt to get settled until his mum found a better job. And Fitz found out about how Simmons' mum had left home when she was only five and she hadn't seen or hear from her since save a brief phone call on Simmons' sixth birthday. 

They balance each other with ease, Fitz's steady, heavy footsteps the perfect counter to Simmons' long, bouncing strides. Where Simmons is often too loud spoken and needs Fitz to pull her back from shouting at the people who upset her, Fitz is too withdrawn and Simmons steps in to pull him to his feet and make him stand up for himself. Even when they're young and have barely just met, their's is an easy rhythm. their friendship quickly becomes like breathing. 

Their respective parents are busy, and it's months and months before they meet for real. It's in an emergency room, oddly enough, after an incident involving the pair of children 'experimenting' with the trajectory of the schoolyard swing set on a Friday afternoon. Simmons jumps too far and lands with a crack, her ankle splintering beneath her. it swells quickly and Fitz panics accordingly. 

"Your flat's closer than mine." she says, calm as she can muster through sharply gritted teeth. She knows enough about bones to know she shouldn't move too much, and mentally counts to ten again and again to try and forget the pain in her ankle. 

"Right. Yeah. Okay. I'll go get my mum. Should I uh.. Should I call your dad from my house? Or just bring my mum back here and take you to the ER and then call your dad? Or?" he's talking a hundred miles a minute but he can't help it because she looks so uncomfortable and scared and helpless and he's terrible with blood and bones and all the strange things she loves so much. 

"Just bring your mum." her voice falters, the confidence she tries so hard to keep up at all times slipping as pain throbs in her leg again "Hurry Leo?" she asks softly, and he nods, sprinting the few blocks to his place as fast as he can. 

"Muuum!" he shouts, banging on the door as he'd left his key in the park, like the idiot he clearly is. "Muuuum! Open up!" he calls again, his voice ragged with lack of breath and worry. There's a stomping on the stairs and the door flings open and his mum looks down, concerned. 

"Leopold? What's the matter?" she looks at him, alarmed

"S'Jemma." he manages to stammer out. "Broke 'er ankle. Need you to drive." his face is beet red from running still and his mother just nods and drives to the playground, where Simmons is sitting on the ground, looking and feeling much smaller than she wants to. Gently, Fitz and his mum manage to lift her into the car, with minimal yelping and crying from Simmons. Fitz refuses to sit upfront, instead squishing himself between Simmons, who is sitting sideways with her ankle up, and the door. He knows she would never ask for him to sit with her, but he knows that also doesn't mean she doesn't want him there. She squeezes his hand when they go over bumps in the road and it hurts his fingers but he doesn't mind. 

As soon as the trio checks in at the ER they call Simmons' dad, who's at work, but he comes as soon as he can, running into the ER in such a production of scattered genius and disarray that's so much likes Simmons that Fitz would laugh if he weren't so terrified of hospitals. Simmons is getting x-rays when he runs in. Fitz spots him right away and waves at him solemnly. 

"Hey, Mr. Simmons. This is my mum, Mrs- uh, Ms-... um. Carol. This is my mum Carol." he stumbles over his words indelicately and his mum extends her hand gracefully. 

"Pleased to finally meet you, Mr. Simmons, though I am sorry it has to be under such unfortunate circumstances. Though I assure you, your Jemma will be fine, she had on quite the brave face and refused to be wheelchaired into the x-ray terminal."

"Please, call me Greg." he said with a terse nod and a slight smile. "Ah, yep, that sounds like my little miss. His eyes lingered softly on Carol's warm eyes and softly curled hair and Fitz looked from him to his mother with slight alarm in his eyes, but any thought he may have had was swiftly interrupted by a nurse emerging to find Simmons' dad and tell them all what was going on. It turned out she had a clean fracture in her fibula, but no surgery would be required, just a cast and crutches. She was waiting for a shot to help with the pain and then she'd go into the cast room. 

"Can I come with you?" Fitz asks quietly as Simmons' dad follows the nurse to the room where she's waiting. He swallows hard as he asks, he hates hospitals and needles and anything medical, but Simmons is his best friend and it's his job to be there for her even if it makes his skin crawl. She would do the same for him after all. Greg nods and smiles, and Fitz pads after him until Simmons comes into view. 

Fitz hoists himself onto her bed and lets her talk about bones and impact fractures and how setting breaks works while the nurse gives her a shot and wheels them both, with an amused smile at pale and pained but confident Jemma and her queasy looking best friend, towards the cast room where Simmons asks for red and yellow stripes, like the colors of her favorite Harry Potter house. 

She doesn't say anything, but she is glad that her dad and Fitz are there. She wants to be a doctor and she loves bones and muscles and the way the body works, but it's different when the body parts are hers and the pain, even if she knows as early as nine it's really just a chemical signal, is in her own nerve endings. She likes that Fitz will listen to her even when what she's talking about grosses her out, and she knows he hates the doctor's but he sits beside her anyway. She holds his hand when they set her ankle, and it's a little bit for him and a little bit for her. 

"Can Leo stay over?" she asks quietly as the nurse helps her to her feet and hands her a set of child sized crutches. 

"'Course he can, if Carol says it's alright." her dad smiles and ruffles her hair. 

The next day when his mum comes to pick him up and take him home, she ends up staying for lunch and Simmons and Fitz watch in a combination of terror and amusement as their parents very obviously flirt with each other. Fitz is the first (and only) person to sign Simmons' cast. He draws little robots holding beakers and magic wands on it in sharpie until Carol finally gets up to leave, taking him with her. 

"So what was that about?" she says easily Monday morning, sliding awkwardly into the desk beside Fitz, her crutches clunking awkwardly against the metal chair legs. 

"You mean our parents? No idea." 

"Would it be so bad if they dated? We'd be able to hang out even more."

"Yeah but wouldn't it be weird if they broke up?"

"I guess so, but wouldn't it be grand if they got married and we could live together?" Simmons said wistfully. She had no siblings, and her mum had been gone long enough that the girl had forgotten what 'family' felt like, and the idea of Fitz being around all the time was endlessly appealing to the young girl. 

"Yeah.. I guess.." Fitz shrugged, his parents' violent split too recent for him to have any faith in the construct of family. He had his mum and he had school and he had Jemma. Why would he need anything else?

Their closeness made it inevitable for their parents' to see each other often, and every time they did they grew more and more talkative and flirtation, until Greg finally asked Carol on a tentative date. They left their children to their own devices at Simmons' house, figuring they couldn't get into too much trouble with Simmons still in a cast for the next week and a half, much to her own chagrin. Fitz and Simmons spent the evening on Simmons' bed with caramel corn and lemonade, watching Classic Who episodes and eventually nodding off about an hour before Greg crept in at midnight, chuckling when he saw them through her open door, fast asleep in a pile of limbs and cast and blankets and empty bowls with Four's voice babbling on low in the background. He pulled a quilt over them and let them be. 

The next weekend, Greg and Carol went out again, and the week after that, and after that, and on and on until it had been nearly a year. Simmons and Fitz were both almost old enough to be actual secondary school students without having skipped grades, and were tied so closely at the hip that the school councilor had contacted their respective parents about their 'budding codependency problems'. 

A little after Leo's eleventh birthday (He's three months and four days older and will never ever let Simmons, who is still taller than him, forget it), Carol and Greg announce that they're engaged.


	2. Some Things Must Change

The wedding between Greg Simmons and Carol Fitz is a quiet affair. There is a best man, Greg's oldest friend Charlie, and a maid of honor, Fitz's aunt. Fitz is the ring bearer and wears a tux that's a little too small, his mother couldn't afford a new one so his aunt did her best to fix up the one he wore a few years before to a family friend's wedding. Simmons wears a pink dress that she hates, claiming the lace itches and that dresses are silly. She refuses to have her hair put up, finally settling on a simple braid after fighting with her father for weeks about it. She walks down the aisle ahead of Fitz, she's the flower girl, and he can't help but think she looks sort of pretty, but he'd never tell her that. Simmons doesn't care about that sort of stuff, standing awkwardly as the few friends of the Fitz family in attendance, only used to Fitz's surly boyishness, fawn over her.

But their parents looks radiantly happy, so the now almost twelve year olds smile at each other from across the aisle as they watch Carol walk gracefully towards Greg. Not much had changed for the pair since they started living together in Simmons' flat after the announcement of the engagement, save for them causing more trouble. Between Fitz's natural knack with anything with an engine and Simmons' fascination with all things with a metabolic process, they caused any number of small fires, large messes, and general chaos. A particularly sterling example was Fitz's efforts to turn Simmons' microscope, more a toy for children than a real microscope, into a more high powered machine than it was. it had worked for a few exciting moments before overheating and catching the table cloth on fire. 

But for the most part, even the chaos didn't phase the happy couple, who were also unbothered by the odd bond their children shared, despite how frequently it was commented upon. Neither of them excelled at making friends, and with both of them perpetually being the youngest children in any given situation, it made perfect sense to Greg and Carol that they would be close. 

In reality, close was probably an understatement, particularly after the two families began living together. Once they no longer had to go home to separate houses, Fitz and Simmons became completely inseparable and one was rarely seen without the other. Certain habits, such as falling asleep in each other's rooms, their parents did try to discourage, but for the most part they were so glad to see their children have even just one friend that they didn't see any harm in it. 

"What do you think will happen to us if they ever got divorced?" Fitz asked one night, his voice low. Greg and Carol had just had one of their rare rows, and Fitz had locked himself in Simmons room with his latest project, dissecting and reassembling a hand-crank powered flashlight to see what else he could make with the same mechanism. Simmons frowned and slipped off her bed, the Harry Potter sheets sliding off behind her as she settled next to her best friend and step brother on the floor. 

"I don't think they will. They don't fight much." Their fights did bother Simmons, but not anywhere near as much as they did Fitz. After all, Simmons had been so young when her parents split, their fights, violent as they had been, were a distant memory. A scar, juxtaposed to the still healing wound Fitz still suffered from his parents' constant battles. 

"But what if they do?" he pressed, stopping his work to worry his sweater sleeves with his fingers. Simmons sighed and leaned her head on his shoulder; her hair which was just starting to curl and wave of it's own accord from the pin straightness it held in her childhood fell messily around her face and his side.

"Nothing will happen to us Leo. Nothing. You'll always be my best friend. Nobody else." To anyone else, it might have sounded like a childish placation, but she knew he knew she meant every word. Call it naiveté, but she had not doubts in her mind they would be friends for the rest of their lives. They were Jemma Simmons and Leo Fitz, a matched set that would never be torn apart. No one would ever understand her as well as he did, so what was the point of trying to find someone who could?

Fitz stared idly at Simmons' knees, still gangly and too bony for her body and skinned and covered with bandaids. She grew too fast to catch up to herself, and she was always tripping over everything, her center of gravity not quite right. She was still taller than him, Fitz having grown barely at all since they met, but he was wider and sturdier than she was, thought his mum assured him he'd grow taller eventually. They were almost thirteen and in just a few months they'd be starting their final year of secondary school two years early, graduating just before they both turned 14.

"Leo?" she asked softly, staring off into space.

"Yeah, Jem?"

"Will we got to university together? I mean, I know we want to study different things but it would be sort of.. strange, wouldn't it? To be apart?" she swallowed heavily, both sure of but still terrified of her best friends answer.

"'Course we will." sounding confused as to why she'd even ask such a silly question. 

"Dad wants me to wait a year. He says fourteen is too young to go off to uni, and I should stay till I'm fifteen." 

"Yeah, mum said as much to me. I bet they talked about it. That's still kind of weird, innit? I know it's been almost a year since they got married but they like, make joint decisions about us and stuff. I think they're worried about us. Not bein' 'normal teenagers' and such."

"Your mum asked me last week if I had any crushes on boys at school. I told her boys who weren't you were stupid." Simmons chuckled as she talked, mentally breathing a sigh of relief at both Fitz's relaxed demeanor and admission that he too couldn't see himself leaving without her. "She looked kind of alarmed, but I mean really, who else at school am I going to be able to hold a conversation with other than you?" she shrugs. 

"I think your dad would hemorrhage if you had a crush on anyone at our school, they're all older than you, and anyone our actual age would never understand anything you were saying." he shook his head and laughed. 

"I can't imagine dating anyone." Simmons says, scrunching her nose and turning her head to stare up at Fitz. "Doesn't it seem weird? Spending all that time and energy on another person? Be like doing what I do with you but with.. not you. Or... I mean.. Not that we're or that I. You know what I mean!" She flushed brightly and pulled away to lean against her bed instead. her and Fitz certainly received the fair share of teasing about crushes from their classmates, not all of it in good fun. But she had no one but herself to blame for then bungle. 

"I err, yeah. I know what you mean." Fitz said after a cough and an awkward pause. "I guess anyway. I dunno. Girls are sort of nice, I think." he shrugged. There were definitely girls in their class he thought were pretty but since he was two years younger than them and undeniably a complete nerd, terrible taste in sweaters included, he knew very well they'd never think about giving him the time of day. 

Neither of them spoke much for awhile. They never really talked about boys or girls other than each other, like they had some sort of unspoken agreement to avoid the subject for whatever reason. While Fitz didn't care much either way, Simmons very definitely preferred it that way. She analyzed everything she could get her hands on and thought things to death, but she didn't like the think about the weight in her chest when her best friend stared absently at the pretty girls in their classes. 

Simmons knows she is smart and she knows she can be good at anything she puts her mind too and she likes herself, but she's also aware of how she feels like a bag of sharp bones and knobby joints that don't fit into her skin, nowhere near as soft and graceful as the other girls around her. She quite likes her hair, long and thick and soft and warm auburn. She doesn't feel ugly, just awkward and graceless, and waiting for the day she finally settles into her own skin. 

Carol sees the idle glances the young girl throws towards Fitz when he isn't paying attention and it worries her, but she writes it off as a childhood crush, after all it's not like the girl has any other good friends, it makes sense she'd have a little crush on the one person it's obvious she feels close to. But she knows her son, and she knows he probably sees his best friend as Jemma Simmons and not specifically as a girl, and it makes her hope the girl's feelings fade away naturally with time and she doesn't have to see the two of them torn apart by an in-congruency in their feelings. 

The glances never quite stop, but she feels relaxed when a year passes and the families are all getting ready for graduation, even though both kids have agreed to wait a year to move onto university, having both deferred admission to the same school. The school guidance counselor gives them a look when they announce their decision to attend the same school, but their parents don't mind, at least they'll have someone who understands them to support them.


	3. Even If It's Slowly

It is graduation day and Jemma Simmons tackles it with the same excitement and enthusiasm she does every new experience in her life. Leo Fitz, who is sitting on the edge of her bed waiting for her to finish combing her hair, however, could not be more terrified. His leg is jiggling nervous and he keeps fiddling with the buttons on his shirt, only looking up when Simmons issues an irritated huff. She tossed the comb aside as she struggled to pull her own thick hair back in a braid for the graduation ceremony, she didn't want it to blow around in any potential wind. After all the last thing she needed was to be blinded by her own hair and trip.

"Let me, Jem." Fit said with a chuckle, standing up. Simmons turned and looked at him, clearly exasperated and then tilted her head suddenly. 

"Leo!" she exclaimed, pointing at him. He furrowed his eyebrows.

"Uh, yes? That's me?"

"Leo, you're taller than me! It only took you, what? Five years?" Fitz cocked his head and chuckled, looking down. She was right, he wasn't sure how he'd never noticed he'd finally gained a good seven centimeters on his step-sister. 

"Well would ya look at that? That's a miracle if I ever saw one." he laughed. "Now turn around, shortie." he smirked and she rolled her eyes but complied, grabbing the comb and handing it back to him. She closed her eyes as he began running the comb through her wavy hair, until all the strands were as smooth as they were ever going to get. With practiced ease, he separated her hair out into sections and and braided it as neatly as possible, without it being so tight it would give her a headache later. He smiled as her shoulders slumped back slightly as his fingers smoothed over her temples to quell any flyaway wisps of hair. Simmons had never been quite able to get the hang of braiding her own hair, but Fitz's hands, flexible and agile from working with small parts took to the task like a fish to water. And despite the vague oddity of the ritual, they both took a comfort in the sensation of his hands in her hair and the closeness the task involved. Fitz loved Simmons' hair. It was long and wavy and sometimes unruly and and warm; as such, it suited her perfectly. He tied the braid off and patted her shoulder affectionately. 

"Thanks, Leo." she said warmly as she turned around, automatically frowning when she saw the knot in his tie. "Goodness gracious, what have you done." she rolled her eyes and untied the offending article with ease before retying it much faster and neater than he could ever manage. She smoothed the front of his shirt and then lunged towards him suddenly, hugging him tightly. 

"Calm down, Jem, it's not like we're going off to school in different countries or something. We're not even leaving home and when we do, we'll both be going the same place. And even if we weren't, we'd see each other at breaks. We do have mostly the same family after all." he chuckled, but there was an edge to it. They were both nervous, after all. 

"I know, I know." she fussed as she pulled back, smoothing the blouse she wore gently. "But it's all so terrifying and exciting even if we're both just going to be home for a year, you know?"

It wasn't long after that that Carol came bustling into the room, fretting over both of them like they were going to prom instead of graduation, and Greg laughed good naturedly from the door way. The ceremony was long, and Simmons had been right, it was incredibly windy, but she managed not to trip as she walked across the stage, and Fitz managed not to shake too much as he shook the headmaster's hand as he claimed his certificate of completion. They both fidgeted in their separate seats for the ages and ages of speeches from teachers and other faculty before the ceremony drew to a close. A few kids gathered and clapped Fitz and Simmons on the back and held brief conversations, but for the most part neither of them were close to anyone from the school, so there wasn't much fanfare until they arrived home and were greeted by their modest but loving family and a large sheet cake bedecked with both their names and several lit sparklers. 

The evening is nice, a low key celebration with the broken bits of both of their families fitting together as best they can. There are gifts given, too. Fitz gets a set of high end tools for metal and electronic work, which Greg and carol must have saved for months to buy. Especially on top of the lab quality microscope they give Simmons, who is so grateful and excited she starts crying. She spends the whole night glued to Fitz's side, some part of her irrationally terrified that graduating from the place they met will somehow change the bond they've forged. She cannot afford to lose him, she learned that long ago. 

They do not sleep that night, deciding to spend the night on the roof of the flat, the air cool but not so cool as to be unpleasant, and they identify all the constellations that they can while laying on a quilt Fitz's nan made years before. 

"It will be strange, being away from home when we go off to school, wont it?" Fitz wonders out loud after Simmons points out all the stars in ursa minor.

"I won't be away from home." Simmons says easily, sleep barely creeping into her voice. Her head is next to Fitz's shoulder, but they aren't touching. 

"How do you mean?" his voice is puzzled as he tilts his head towards her, focusing on her face instead of the stars. She shrugs. 

"I'll be with you, won't I? I reckon I could feel at home on an alien planet as long as we were together. Sure, I'll miss my room and my dad and your mom and it will be weird to do things for myself. But you'll be there, so it will be okay." she speaks with a confidence Fitz can't even comprehend, as someone who has lived his life questioning everything around him. Second guessing became second nature, and the steady confidence Simmons has in him, and herself, and their friendship, and the world him captivates and confuses him every day. 

"I suppose you're right." he answers with a nod, his voice more even than the vague terror that flutters his heart. He sees a moment of doubt flash clearly in her eyes and he reaches for her hand, squeezing her slight fingers in his. As always, he's not sure if the grip is for his benefit or hers. He thinks at some point it stopped mattering, and he lost track of where he started and she began. 

When he directs his gaze back at the sky, Simmons allows herself a moment to stare at Fitz's face and smile at the way the moonlight lights his curls so softly. he hates his curly hair, always complaining it never does what it's meant to and looks too messy, but Simmons thinks it's perfect. After all, she knows Fitz isn't as even and perfect and exacting as everyone thinks he is, and she likes to think of his hair as a tiny bit of his more natural personality sneaking out. Sometimes she thinks she might be in love with him, at least a little bit, when he's braiding or hair or laughing that certain laugh or doing any of the things she knows only she gets to see. She knows he's her best friend and her step-brother, something most people would frown on, but she can't help the lightness in her chest when he says her name that certain way or catches her eyes in a crowded room to laugh at something only they find funny. Leo Fitz has consumed her very existence, and she knows on an intellectual level that that's probably unhealthy and it will likely lead to ruin, she can't ignore how very right it feels to let him be her everything, even if all logical signs point to disaster. 

Fitz spends a lot of time rolling the words sister and best friend and step-sister around in his brain, trying to find a word that fits. He has a brother, even if it's been years since they spoke, so he knows what it's like to have siblings. But he reckons a sister and a brother aren't the same thing, so he's never sure if Simmons fits in that box or not. Step-sister should seem obvious but the step makes it feel so cold and informal and wrong for a relationship he cherishes so dearly and that is so warm and bright and full. best friend should also seem obvious, but sometimes he feels like the phrase is inadequate to describe the bond between them. He tells a stranger once who asks that she's his sister, because it's not technically a lie and he didn't like the way the older man looked at her and protectiveness flared in his chest in a way it hardly ever did, and it seemed like the safest answer, like the answer that would make him leave. But the word feels strange on his tongue and settles oddly in the pit of his guts and the back of his mind. 

They watch the sunrise in silence, Simmons moving to let her head rest of Fitz's shoulder, he neck tired from straining on the wooden roof all night. They creep down around eight am, as silent as possible, and sneak into Fitz's room before their parents can wake up, dozing off on the floor in the middle of an episode of Fringe they started watching on his laptop. Their parents wake them gently a little after one pm, with pancakes and bacon and tea and the teenagers smile sleepily and pad into the kitchen to eat, a ease of silent communication flowing between them as they ate. 

Simmons reaches over and rubs a spot of jam off Fitz's face with her thumb and he rolls his eyes but lets her and she smiles softly before returning to her own meal. Carol narrows her eyes for a moment but eventually shook her head, Simmons had always been a little on the doting side. It was probably nothing.


	4. And Confusing

Greg Simmons worries about his daughter. She has sparse few friends from school and science camp, but she never seems to hang around them much, preferring her books and her microscope and Fitz. She spends time with them on occasion, most of them boys, but never anyone she shows an inkling of interest in. He tries to remind himself again and again how young she is, because she thinks so much older than she really is, and she has plenty of time to grow and change and socialize. But he is a scared old man afraid of his daughter making the same mistakes he did, always putting work and knowledge and matters of the mind over matters of the heart. It ruined his first marriage and Jemma’s childhood, though she’d have to have been held at gunpoint to admit the constant fighting and terrible divorce had been anything other than a minor inconvenience. Most of the time she claims she simply doesn’t remember, she was too young. But he can tell in the way loud sounds make her wince and how outside of Fitz she shies away from emotional attachment that some part of her remembers, whether she knows it or not. 

During her gap year, Simmons spends a lot of time in the community college library. Fitz flits between there and the local electronics repair shop, helping out for no pay just for something to do, since he isn’t old enough to legally hold a job. 

Their parents had thought maybe time out of school, when they weren’t forced to be together every day by being in the same classes, might put some distance between them, but it seemed to have done the opposite. If anything, they spent more time together than ever, often taking over the entire coffee table and a good portion of the living room floor for days at a time with text books and notes and haphazardly assembled lab equipment Fitz makes Simmons out of kitchen appliance pieces from the junk bin at the shop. Their years of friendship have given them an eerie synchronicity that seems to border on them being literally psychic. If Simmons’ hair falls in her face while she’s using her hands, within seconds of it slipping Fitz has pulled it back behind her ears, wrapping it with a rubber band from one of their pockets. When Fitz’s shirt sleeves unravel while he’s tinkering with something, moments later they’ve been rolled up by Simmons, sitting neatly at his elbows. 

They spend a lot of late nights on the roof or in the front yard, tracking the movement of the stars for fun and talking about light pollution. Simmons implores Carol to teach her how to cook, deciding it would be a useful skill to have when they aren’t living at home. When she says ‘they’ Carol wonders if one of them ever makes plans without considering the other, but when she looks back and Fitz is smoothing the flyaways in Simmons’ ponytail and she’s straightening his shirt collar in an idle, habitual way, that the thought would probably never even occur to them. 

It turns out Jemma Simmons has a knack for cooking, which she decides is logical since she wants to be a chemist after all, and cooking is just a specific kind of chemistry. Carol teaches her old Scottish recipe and helps her with the English and Italian and french ones she finds online and decides to tackle, and by the time summer has rolled to a close and the nights are getting cold again, she could probably cook just about anything you put in front of her. She hasn’t quite mastered baking, but that’s okay because Fitz can bake just fine.

While Fitz is making friends with the middle aged men in the electronics shop, Simmons manages to infiltrate a study group in the local library of local university students, much to her delight. They’re older and almost as brilliant as she is and they seem to genuinely like her. Fitz tags along sometimes and they take to him just fine too. Fitz doesn’t mind, socializing in small doses is fine, and one of the girls in the study group has long dark hair that swings around her shoulders in the prettiest way. It makes Simmons’ stomach sink when she sees him staring at the girl, but she puts it out of her mind because at the end of the day she wouldn’t trade her friendship with Fitz for anything in the world. 

That year Simmons spends a lot of time wondering what it would be like to kiss Fitz, whereas Fitz mostly just wonders what it would be like to kiss. Oddly enough, Simmons finds out first when a boy she graduated with asks her on a date before he leaves for school. She says yes, because it seemed like the right thing to do, and he was always rather nice to her. Greg protests at first, but Carol knows the boy’s mom, so he decides to let her go. After all she’ll be out of the house in a year, he might as well let her get used to freedom now so she doesn’t abuse it, not that she ever would. Even though Fitz went to school with him too, he spends the whole night locked in his room pacing, worrying about the entire situation much more than he needs to or should. 

He drops her off at the door after dinner, and 9:36, and he gives her a simple peck on the lips. Simmons doesn’t feel fireworks or much of anything but she supposes it was nice enough for a first kiss. When she gets to her room Fitz immediately barges is demanding to know why she was five minutes later than she said she’d be and she laughs and wraps him in a hug. Fitz will always be Fitz, and she loves him for it. 

Later in the year, Fitz stutters his way through asking out a girl who was a year below them in school. Simmons spends the night at a friend’s house, the silence of the house knowing he was on a date too much for her nervous tendencies to bear. At the end of the night Fitz kisses the girl and it’s nice but nothing special, though for whatever reason he feels better having done it. 

"Are you scared?" Simmons asks him one night, mere weeks before they leave for Oxford, huddled on the roof on an unseasonably cold night. She thinks the sweater she’s wearing might be his, but she’s not sure, they’re mostly the same size and she still tends to wear her clothes loose. 

"Terrified." he says without hesitating. He leans back on his hands, staring up at the clear sky. 

"D’you think people will like us okay?" her voice is quiet and she leans her chin on her knees, fingers tugging at the hem of her worn blue pajama pants. 

"Like you need to worry about that, Jem. Everyone loves you. S’me who’s got to worry." he chuckles dryly.

"Oh please Leo, people like you plenty. ‘Sides, even if they don’t you’ve always got me." 

"S’all I need really." he says, and his voice is low and she wouldn’t have heard him clearly if her ears weren’t so used to the sound of his voice. Some distant part of her chest glows warm before she stifles her feelings down. Distance is safer, after all. His fingers are drumming nervously on the roof and she reaches over and stills them with her own. He turns his hand to wrap around her fingers and it’s more like a reflex than a conscious decision. 

Simmons doesn’t think there are words to describe what Fitz is to her. She knows he is her best friend and her step brother and she knows she is in love with him, but any combination of words she strings together never seems adequate. She would rather describe their friendship by the way she doesn’t need to ask him to help with her hair in the morning, or the way he doesn’t have to ask for help with his tie, or the way when she sits close enough to feel the constant warmth he radiates, she loses track of where one of them stops and the other starts, her giving where he took and the two of them breathing in continuous rhythm. 

Packing up to leave for school at the end of the year is strange. Simmons keeps finding Fitz’s jumpers and t-shirts in her drawers, and Fitz’s room is littered with Simmons’ headbands and hair ties. Simmons can’t help but tear up, unable to shake the feeling of something ending even though they’ll be home at Thanksgiving and Christmas and she’ll still see Fitz nearly every day. Fitz is sad too, but he has settled quickly and easy into stoicism, and only Simmons can read the nostalgia and reluctance in the clench of his jaw and the set of his brow. 

They clutch hands in the backseat of the rented moving van the entire drive to the university. Neither of them remembers who reached out to the other first, but it doesn’t really matter because his pulse will always pick up where hers ends.


	5. And Sometimes Messily

Living away from home is strange, more so for Simmons than for Fitz. He already moved from one country to another after his family was torn to pieces, Simmons stayed in one place her whole life. But as always, she meets the challenge head on and with enthusiasm, and if Fitz hadn’t known her for six years, he would have no idea she was scared at all. Moving into their dorms, in the same hall but with different rooms, since freshman dorms have co-ed halls but not rooms, takes all day. Fitz’s roommate seems quiet and polite, and Fitz is relieved. Simmons’ roommate is social and boisterous and nice, but out-going enough to make Simmons nervous. Felicia already seems to know half their halls, and Simmons feels very small and young compared to her.

As soon as Simmons hangs her last poster on her side of the room and finishes tucking neat hospital corners into her dark burgundy sheets (She has her old Harry Potter sheets tucked in the closet, she loved them but couldn’t bring herself to seem even younger than she already did.), she ducks into Fitz’s room. He’s fussing with his sheets, trying to tuck them in neatly but keeps mussing them. 

“Here, let me.” Simmons lays a hand on his shoulder and smiles, and he heaves a sigh of relief. Not just that she’s there to help with his sheets, but because if she’s popping into his room to check on him, nothing has changed yet even though they’re separated by several doors and not just a wall. 

“How’s your room shaping up? Neat and tidy as always I assume?” he asks, setting into a desk chair while she smoothed his blue plaid comforter over his flannel sheets. 

“A clean workspace is an efficient once, Fitz.” She says with a terse nod, fluffing one of his pillows. She uses his last name, and he knew she would, but it feels weird to hear her say it. In the car on the way to Oxford, she’d decided they’d sound older and more professional going by their last names, at least around other people. He wasn’t sure why it mattered but he relented, mostly because he couldn’t ever say no to her. But he knew he’d always call her Jemma or Jem when it was just them. Her name suited hers, Jem like gem, something important and precious and valuable. Better than his suited him, at any rate. Leo short for Leopold, meaning lion or lion people, symbols of bravery and power, two things he most definitely did not possess. 

“More like a boring workspace.” He countered, rolling his eyes. His roommate coughed. “Oh, right, um, Je-Simmons, this is George, my roommate. George, Simmons.” He nodded towards her awkwardly, not liking the way her last name rolled off his tongue. 

“Hello! Simmons is my last name, obviously, but I find it much better suited than my first name, so.” She shrugged and extended her hand. 

“So you’re the girlfriend then?” George asked as he shook her hand, raising one eyebrow. Simmons spluttered loudly, her eyes widening while Fitz flew into a coughing fit, shaking his head. 

“No, um no, she’s uh, Je.. Simmons is my sister, I mean step-sister. And best friend. Since we were nine.” He’s babbling and his face is bright red and he’s not sure why. Simmons on the other hand is as white as a sheet and looks like she wants to die right in that spot. 

“Yes, exactly. Step-siblings. Parents happily married for… three years now? Something like that. I’ll be going now.” Her posture as stiff and she nods awkwardly before almost sprinting back to her room. 

“I assume she’ll be around a lot?” George raises an eyebrow again, staring at Fitz skeptically. Fitz swallows and nods. 

“Yeah, uh, we’re close. Best friends and step siblings and all.”

“You Scottish?”

“Yeah. Moved here when I was nine. Well not here here. But. England. Simmons’ dad and my mum got married we were almost twelve.”

“Wait, they got married three years ago. Are-“

“Oh, right, yeah. We’re fifteen. Child prodigies and all. I’m an engineering major and Simmons is a biochem major.”

“Holy shit, you’re like a baby. Jesus.”

“Yeah yeah yeah, trust me, I know. We actually graduated a year ago and deferred admission for a year, parents’ wanted us to wait to move out.” There was a timid knock on the door.

“That you Simmons?” Fitz called.

“May I come in?”

“ ‘Course ya can.” He rolled his eyes as the door creaked open.

“Sorry about my hasty exit earlier.” She nodded politely to George before turning to Fitz “Fitz, your mum and my dad are out in the quad, they want to go out to dinner before they drive home. We’re welcome to bring our roommates, if you wish to come, George, though Felicia has opted to find her boyfriend and spend time with him.” 

“Nah, I’m good, but thanks for the invite.” George nods back before picking up a book and flopping onto the sofa.

“Well, later then,” Fitz imparted, before Simmons hooked her elbow through his and lead him down the hall, already chattering excitedly about classes starting the next week. 

After a long, loud family dinner and long tearful goodbyes, Greg and Carol leave a tight-lipped Fitz and a teary Simmons at the entrance to their hall. Simmons sniffles. 

“C’mere you big crybaby.” Fitz rolls his eyes, pulling her towards him easily. She wraps her arms around him tightly and he holds her up, but he’s resting his weight against her as much as she is against him. He smells like peppermint soap and she smells like almond shampoo and together they smell like home to each other. 

“I know I’m meant to be the adventurous one but I’ve never been away from home for more than a few days before.” She mumbles, voice caught up in the cloth of his sweater. 

“Hey now. You’re not away from home remember? I’m right here with ya. Fitz and Simmons, Simmons and Fitz, Jemma and Leo. We’ve always got each other.”

They power through a week of hall bonding rituals and school shopping and adapting to being away from home. Simmons spends most of her days in Fitz’s room, still adapting to having such a sociable roommate. 

When classes finally start, Simmons is sitting at her desk fidgeting with the layout of her pencils and pens and laptop in her messenger bag when there’s a knock on the door. She recognizes the cadence and leaps up before her roommate can even move from the sofa where she’s sitting, browsing her laptop. 

“Fitz!” Simmons says brightly, immediately wrapping her arms around him in a hug. She can feel the tenseness in his shoulders as she lets go and ushers him in. “Oh, right! Felicia, Fitz, Fitz, Felicia.” She says brightly before turning to Fitz and grinning. “You need me to tie your tie don’t you.” She chuckles. Fitz shrugs and nods. 

“You do it better than I do.” He smoothes her hair out. “D’you want me to redo your ponytail for you? It’s a bit of a mess, Jem.” She gives him a look for using not only her first name, but a nickname she doesn’t even tolerate from anyone but him, but then nods. 

“Please, but let me fix your tie first.” 

Her roommate stares in bemusement as Simmons tied Fitz’s tie into a neat Windsor knot and fixed collar so it was straight, and with even more confusion as she spun around and handed Fitz a comb, allowing him to re-brush her hair and pull it back neatly, tucking the too short strands of her bangs behind her ears. 

“There you go. Pretty as a picture.” He drew out the ‘r’ in pretty with the brogue of his accent and grinned when it successfully drew a smile and a laugh from her. 

“You never mentioned you had a boyfriend, Simmons.” Felicia called as she tossed a book into her backpack. This time Simmons turned bright red and would have been frantically shaking her head, if Fitz weren’t still fiddling with her ponytail. 

“We’re just friends!” she managed to strain out, just as Fitz babbled off “I’m her step-brother!” and promptly let go of her finished ponytail. 

“Oh, um, sorry for the confusion then.” Felicia said with a nod before quickly ducking out of the room.

“Why do people keep asking that?” Fitz ran a hand through his hair, clearly exasperated by the ordeal. 

“Who knows. Obviously people just can’t tell the difference between a close platonic bond and romantic love.” Simmons shrugged, but her voice was strained. Fitz could tell but something about the set of her shoulders told him not to push it, and instead he opted to push her, lightly, by the lower back.

“Well, bollocks to them, let’s go to the dining hall so we have time for breakfast before class eh?”

Over their first few weeks of class, the number of people who mistake Fitz and Simmons for a couple skyrockets. A few people mistake them for actual siblings, and one of their teachers jokingly refers to them as Fitzsimmons when calling out partner assignments, saying she wouldn’t dare separate the pair of geniuses. The name sticks after that, and the two have earned a nickname that reflects the twoliness of their shared existence. All in all, school is nice. They’re finally among people as smart and invested as they are in education, and they take to all of their classes, the ones they have together and the ones they don’t, like a fish to water. Simmons spends a lot of afternoons in the quad, thrilled to bits by the tree she knows was used as the base for the Whomping Willow and the fact that she can sit underneath is and take notes for Intro to Advanced Biology. Fitz tags along sometimes, but generally opts to hang out in the lab or his bedroom. 

The majority of their peers seem to regard them as a single entity, which never really fazes Simmons and only bothers Fitz sometimes. Every once in awhile there will be a girl he admires, and even though he knows it’s because he’s so young, he can’t help but at least blame, at least a little, the fact that everyone thinks he’s in love with his best friend and step sister, or at least too closely tied to her to bother dating. Simmons draws more attention from boys than he does girls, her more outgoing nature lending to her seeming older, but she’s never particularly interested. She’s taking so many classes and she enjoys all her work so much, and of course there’s the matter of her being in love with Fitz, but she tries not to think about that too hard. His crushes on other girls don’t bother her as much as they did, because as long as she’s his best friend, she knows she holds a place in his life no one else can ever inhabit. 

When exams roll around for the first time, they fall into an easy routine of studying in Simmons’ room, since Felicia often vanishes to stay with her boyfriend. They’ll be up until the early hours of the morning, then creep out of the hall to walk to the convenience store down the road for ice cream or candy bars or crisps and go back to Simmons’ room and curl up on the sofa with tea and snacks and fall asleep in front of Doctor Who or X-Files or whatever else they’re watching on Netflix at that moment. There are any number of mornings Felicia walks in on them asleep on the couch or in Simmons’ bed or even on the floor, surrounded by textbooks. They tell her half a dozen times that they aren’t dating, and for goodness sakes they’re practically related and while it’s weird that they’re step-siblings she never quite believes them. 

Fitz’s roommate still has no idea what the make of the pair. Some mornings without even being prompted Simmons will appear in their room and fix Fitz’s clothes and turn around so he can braid her hair or fix her ponytail. They speak in tandem sentences, one of them picking up where the other lets off and have absolutely no concept of personal space. He’s never seen two people so strangely in sync before. It was like they’d forgotten how to exist separately, and each of them had movements and thoughts and breaths that were completely dependent on the other’s.


	6. Or Unexpectedly

Before they know it, exams have ended and they've passed with flying colors. Not that they ever expected not to. The residence hall is a blur of people packing and celebrating. Fitz and Simmons are walking into the dining hall the day before their parents come to pick them up when it happens. 

Neither of them notices, but when Felicia, sitting at a nearby table and eating a sliver of toast, starts laughing and her boyfriend lets out a hoot and points, Simmons swallows and looks up. Fitz follows suit and visibly wince. 

"Oh, bollocks. Well this is just grand." he mumbles under his breath. Simmons sighs as she stares at the sprig of mistletoe over the door they're both standing in. 

"They're never going to let us live it down if we run, you know that. Might as well grin and bear." she says evenly, though her inner demeanor is anything but. He clearly doesn't want to kiss her and while she's not surprised, it still breaks her heart, just a little. "I know I'm hardly one of the beautiful dark haired girls you're always swooning over, but kissing me for a second has got to be less of an embarrassment than us running away like children." Fitz frowns then, realizing all of a sudden that his hesitance read as him not wanting to kiss her because of her, and not the situation. Not that he wants to kiss her. He doesn't think anyway. Jemma Simmons confuses Fitz more than mostly anything in his life. 

"I didn't mean it like that, Jem." he shakes his head and then shrugs, leaning his head down the couple of centimeters to hers and kissing her lightly. It only lasts a moment before they pull away and continue into the dining hall as if nothing has happened. But something most definitely did. 

Simmons cannot hear the din of the dining hall over the sound of her blood rushing in her ears. There was not a millimeter of doubt left in her mind. She was in love with Fitz. Nothing would ever come of it, but she didn't mind so much. He was something to him that no one else would ever be, and that was enough for her. 

Leo Fitz is terrified. More than anything in the world, he hates change. Especially unexpected change. Which is why he has been vehemently ignoring most of his feelings since the age of twelve. He's far from stupid, he can see the similarities in the girls he likes. The wavy dark brown hair, or the warm hazel eyes or the way they're always just barely shorter than him. But Jemma Simmons is his best friend. His only real friend. And their parents were married for god's sakes. Not that that actually mattered, he knew that, but it still seemed weird to him.   
But he can't act weird around her because he knows her and if she thinks he's pulling away she'll freak out but he doesn't want her to figure out what he's thinking either. He can't lose her, it's not an option. He wouldn't know what to do without her in his life. 

The next morning they sit on the steps, snow falling softly above them, and wait for their parents to come by and pick them up. Fitz glances over at Simmons and almost smiles, before he fights the expression down. She'd stolen one of his sweaters, not that that was an unusual occurrence. He figured he'd lost about three sweaters to her since they came away to university, and when they packed up to come in the first place she'd surrendered about five from her room. The particular sweater she was wearing, thick and cable knit and a dark navy blue, he hadn't seen in a few months. She'd probably taken it back when they lived at hime and never given it back. He didn't really mind. There was always something reassuring about how comfortable she felt taking his clothes. Especially now, with his feelings all bungled up between his chest and his head from the day before. 

Simmons has mostly settled back into normalcy after the kiss the day before. Fitz is acting sort of strange, but she writes it off as general Fitz weirdness. She takes note of the fact that he obviously knows it's his missing sweater she's wearing but doesn't say anything. She likes wearing his sweaters. They remind her of him. Warm and familiar and sturdy and soft. 

"Ready to go home?" she leans back on the steps as she asks, looking up to watch the snow fall softly. 

"Yeah. I mean, I like it here and all but. It'll be nice to back for awhile. See mum. All that stuff."

"Plus, Christmas is always nice." she pauses, looking over at him. "F-... Leo?"

"Mm?"

"We're alright, aren't we?" her voice sounds small and insecure and generally unlike her and Fitz feels his heartbreak a little because he knows he's being strange and it's his fault. He scoots over on the steps and grasps her hands tightly for a second. As always, he's greeted by the sensation that when they touch there's no longer anything between them, nothing separating his soul from hers. If he believed in souls, anyway. 

"Of course. We will always be alright." he doesn't say that they have to be alright, he wouldn't know what to do if they weren't alright, but he doesn't need to. She feels it too. She nods and rests her head on his shoulder for the rest of the wait and he ignores the way he feels too light, like he might float away, when she lifts herself up to get in the car. 

Fitz tries his best to act normally the whole time they're home, but it's tough. He knows Simmons can tell, but also that she believed him when he said they were fine. Mostly, they are too consumed by Christmas preparations to think too hard about much of anything. Simmons helps Carol cook, and Fitz bakes dozen upon dozen of cookies, including sugar cookies Simmons helps him decorate, though it quickly dissolves into the two of them trying to draw on the other's face with the icing until both of them have to spend half an hour in the bathroom trying to get the food dye stains off of their skin, giggling the entire time. 

On Christmas morning, Simmons is beaming as she waits for Fitz to open her gift. It's a small box, and inside it is a small stuffed spider monkey, Fitz's favorite animal, and a fancy envelope. He perches the monkey in his lap and tears the envelope open carefully. When he opens the letter and reads it, his mouth falls open a little and he shakes his head. 

"I can't believe this." he says quietly.

"It was the best I could do. I could hardly buy you a real monkey, so I thought this would be the next best thing. They let you name it and everything. As you can see I've told them to call it Coolidge, after the man who invented the x-ray tube, but I'm sure you can change it if you want." Fitz shook his head emphatically and practically jumped over towards her, wrapping her tightly in a hug, his face pressed into her shoulder. 

"It's perfect. You adopted a monkey in my name, it's absolutely perfect and I love you for it and you're the best friend in the entire damn world Jem. Thank you." his words are babbled and muffled by her shirt but she hears them just the same and returns his embrace. 

"I'm glad you like it, Leo." 

"I love it. Now open yours even though it's nowhere near as perfect."

He sat back slightly, leaning on his heels as he watched Simmons peel the paper from the small package in the same careful way she did everything. She looked at him when she got the paper off and squinted, confused. 

"Open it." he said, a hint of smug confidence in his voice. She raised an eyebrow but flipped open the cover of the hardback copy of Prisoner of Azkaban that had been under the wrapping paper. She nearly dropped it when she got the acknowledgements page. 

"Oh my god, Leo. When did you even find the time." her fingers touched the pages almost reverently a soft smile on her face as she read the words scrawled therein black ink.

"D'you remember a few days after the fifth book came out when I vanished all night? Said I had a date? I was waiting in line at the local bookstore where she was doing a signing. I figured the third book made the most since, I know it's your favorite." 

She traced the signature one more time, rereading it slowly.   
For Jemma,   
May you always find and conquer any adventure you seek. Make Hermione proud.   
Love, JK Rowling.

Shaking her head again, she places the book gently on the floor and lunged at Fitz hugging him tightly. 

"It's perfect. You're perfect. Thank you so much."

The rest of break passes without incident. Simmons and Fitz spend the new year on the roof, huddled in blankets and sweaters to ward off the cold, with the mugs of hot chocolate and brandy their parents allowed them to have to celebrate their first new year as college students. Neither of them has ever drank before and after two cups the world is fuzzy enough around the edges for them to have cuddled together against the cold and watch the seconds tick down on Simmon's phone. When the clock hits midnight, the neighbors are lighting off fireworks. Fitz turns to Simmons to wish her a happy new year but when he sees her, staring at the fireworks, rosy cheeked and smiling and with snow in her hair, he kisses her instead, too tipsy to care about the consequences. 

In the morning they remember. but they both pretend they don't and there's a distinct air of awkwardness between until the pack up to go back to school three days later.

**Notes for the Chapter:**

> Six chapters in and there's finally a kiss. You go, you crazy kids.


	7. And Sometimes That Change

It's strange to feel this awkward tension. Even when Simmons was falling head over heels in love with him, everything was easy because she understood, or thought she understood, exactly what they were to each other. He was her best friend, and she was his. She loved him, he thought of her as a sibling or a close friend or something else utterly platonic. The kiss under the mistletoe, as nice as it was, had been nothing. It had been a joke, a silly situation brought on by peer pressure. But what about the kiss on the roof? What had that meant? He'd kissed her, after all. Was he simply looking for someone to kiss at midnight and she was the only one there? She shook away the thought immediately. That wasn't like Fitz. He wasn't one to be cruel in that way. 

Simmons let out a groan and pulled her pillow over her head. After a few minutes of staring at the burgundy pillow case at close range, she threw it away from her with another groan and flopped onto her side, staring grumpily at her small set of drawers next to her bed. This of course did nothing to relieve her puzzled thoughts, as on her nightstand were no less than three pictures of her and Fitz, and the autographed copy of Prisoner of Azkaban he'd given her for Christmas, and an incredibly worn hand woven friendship bracelet he gave her when they were twelve. Closing her eyes, she turned back onto her back and counted to one hundred as slowly as possible, trying to move the focus of her mind to literally anything else. It worked, a little anyway, and she rose to her feet to grab her books and begin studying for the new term. Her newfound determination to not think about Fitz crumbled the moment she opened her notebook. Fitz's scribbled equations and jokes and comments were written in his neat, blocky, all-caps writing all over her notes from the end of the previous term. 

"Oh, bugger it all!" she yelled out loud, before slamming her notebook shut dramatically and throwing herself back onto her bed.   
"Are you alright?" the door creaked open and Felicia walked in, grocery bags in hand as she stooped down to load the mini-fridge with soda cans and string cheese and a few tubs of yogurt.   
"Who, me? Right as rain, never better?" Simmons flush and quickly pretended to open her Intro Physical Medicine text book and read intently.   
"Where's Fitz? Trouble in paradise?"   
"He's just in his room. We don't have to do everything together, we are separate beings, after all!" Simmons winced as soon as she stopped speaking and dropped her head to her knees. "Sorry.. that was rather snappish of me. I'm just a bit on edge, that's all."   
"Well, I know we don't talk all that much but if you need some advice I can lend a hand? You seem like a sweet smart kid, but something tells me you don't have too much experience in the romance department." the older girl shrugged effortlessly and pulled the tab on a can of diet Coke before flopping onto the tiny sofa.   
"I've never really felt the urge to date. Never seemed necessary."   
"Because you're in love with Fitz. right?"  
"How'd you guess?" there's a level of resignation in Simmons' voice as she looks at her roommate, her eyes tired.   
"It wasn't difficult. How long?"  
"I'm not sure. Twelve? Thirteen maybe? Sometime around there."   
"Wow. Young."   
"Fitz is.. Fitz is sort of my only real, close friend. When you're two years below everyone else in your classes because you skipped multiple levels, it's a bit hard to get on with people. Then Fitz transferred into my secondary school when we were both nine and my whole life changed. No one had ever... tried so hard to be near me, or understood me so well and so easily before Fitz. I'd have been miserable in school without him."  
"So what happened? THis isn't because of that silly prank with the mistletoe is it?" Felicia winced apologetically, but Simmons shook her head.   
"No, no. I mean it was weird for a bit but we were fine by the time we got home. No it was New Years that mucked everything up. Fitz and I, we sit up on the roof of my flat a lot, we both like tracking the constellations, we've been going up there for years. So we were up there on New Year's eve so when midnight hit we could watch the neighborhood fireworks. And my dad and his mum let us have a bit to drink so things were a bit fuzzy around the edges. And it hit midnight and we were watching the fireworks and then suddenly he kissed me. Not much, just a little, and then almost immediately he went back inside and we're now basically both pretending it never happened." Simmons hugged her knees. Felicia sighed softly.   
"I wouldn't worry about his feelings for you, if that's your problem. I would bet my scholarship that boy has feelings for you. He looks at you like you made the universe with your bare hands. It's kind of sweet, actually. That's why I put the mistletoe up, I was hoping maybe if you two kissed it would make him tell you how he felt or something. I would just talk to him. I know that seems like the obvious solution and I'm sure you've thought it up yourself but it's really the only thing to do with situations like this. Plus, you two are so close. I doubt this could end your friendship, but it's only going to get worse if you let it fester."  
"You're right and I know you're right but it's just. Terrifying. Even if he does care for me... in that way, it's terrifying. Won't our parents think it's weird?"  
"If either of you have a mum or dad half as smart as you are, they figured it out years ago. Plus, they got married after you were already friends and when you were older so there isn't really anything wrong with it. Kinda weird, yeah, but I've seen weirder."  
"Thanks, Felicia."  
"Hey, not often I get to give advice to a genius, right? Anyway, I'm gonna take off for awhile. Good luck, kay?" Simmons nodded at her and Felicia left. Simmons promptly rolled over and screeched into her pillow 

Over in his dorm room, Fitz was not faring much better. He was currently nursing a bruise on his hand from early new year's morning. When he'd left the roof after kissing Simmons he'd promptly gone into his room and hurled his fist at the wall in frustration. Nothing has broken, so he'd simply worn baggy jumpers so no one would notice. Simmons did, of course, but she just looked at him sadly and started to walk towards him, only to look let down when he turned away and walked off. It was a mess between them and it was entirely his fault. 

"I am a BLOODY GENIUS how did I do something so DAMN STUPID?" he groaned loudly, his head thumping against his headboard. His roommate chose that moment to announce his presence in the doorway by clearing his throat. "Oh. Sorry George, uh, carry on." Fitz winced at his own dramatic display and immediately begun fiddling with his phone. 

"You okay mate?"  
"Yes, clearly all is well in the world of Leopold 'Complete Fucking Dunce' Fitz, as I sit here screaming at nothing, I just smash my head into things for fun." he rolled his eyes and rested his head in hi hands with a groan.  
"Do you want me to go get Simmons?"  
"Do NOT go get Simmons, she is the last person I want to see right now! Okay no, that's I lie, Simmons will always be the first person I want to see in the world which is the entire problem in this situation and seeing her would solve approximately nothing." his irritation made his accent thick, and George had trouble making out what he said at first, but it clicked after a moment.   
"So it's about Simmons. You're uh.. step sister." he said the word 'step sister' with a certain measure of amusement.   
"Yes, my brilliant genius step-sister who I decided it was a great idea to drunkenly kiss on a rooftop on new year's eve, thus ruining what is essentially the only significant relationship I've had since I lost contact with my brothers."  
"So go talk to her. Tell her how you feel."  
"I can't date her, she's my step-sister. If we dated and broke up it would ruin our parents' lives. Also we're only barely about to turn 16, there's no way we'd stay together more than a few months, a year at the longest, and it would ruin our friendship."  
"Well aren't you a pessimist."  
"I'm not a pessimist, I'm realistic. Sixteen year olds don't stay together forever."  
"Some do. If you love someone I don't think it matters when you meet. My parents met in secondary school and they're still perfectly happy."   
"Yeah, well my parents met in secondary school and then my father up and left and ruined all our lives and broke my mother's heart."   
"Doesn't mean you'd do that to Simmons."  
"How do you know I'm not afraid she'd do that to me?" Fitz quipped, frowning.   
"I've lived with you a few months now. I see how you work. You'd never worry about Simmons hurting you, you know the thought would never occur to her. You're worried you'll hurt her. You're hardly the only male in the world afraid of repeating his father's mistakes." George shrugged and took a bite of apple. "Besides." he mumbled as he crunched. "Letting this sit and get worse is way more likely to mess up your friendship that trying to date and actually talking your feelings out with her. I say you go talk to her. And I mean go to her and talk, I promise you the chances of her coming here are slim. That girl was clearly in love with you, and she's terrified you'll reject her. She's not gonna seek that pain out herself."

Fitz leaned back again, squeezing his eyes shut and trying to let George's words soak into his brain. Did he love Simmons? What a stupid question, he thought. Of course he did. He'd always loved her. Just because he'd spent years vehemently ignoring his feelings for her didn't mean they weren't always there, burning brightly somewhere in the background, flaring in his chest whenever she smiled or called him Leo or fixed his tie or leaned against him or, for that matter, really just sort of existed in his general vicinity. But was it worth the risk? Love had ended terribly for most people he knew, and Fitz was a believer in nothing if not statistics and trends. but he couldn't overlook that while rare, outliers did exist. He just didm't want things to end poorly between them and lose her friendship. Though if George was right and she was sitting and waiting for him to reject her, he might lose her anyway if he doesn't say anything. With a sigh, he steeled himself and stood, leaving his dorm and walking down the hall. He did something he'd literally done before when entering Simmons' room. He paused, hesitated, before knocking just loud enough to be heard. There were soft foot steps and the door swung open to reveal Simmons, looking tired and disheveled and maybe like she'd been crying a little but also as radiant as ever. 

"Hi." he said, his voice tight.   
"..Hey."   
"Can I come in?"  
"Of course." she nodded stiffly, stepping aside to let him in. His eyes paused for a moment on her nightstand, with the book and bracelet and old pictures of them arranged neatly there, beside her reading lamp. He ran his hand up the back of his neck, tugging at his hair.   
"We should probably talk about, uh, some stuff." 

Simmons swallowed hard and nodded.


	8. Turns Out It  Was Exactly What You Needed

Simmons swallowed hard, sitting awkwardly on the edge of her bed. Her nails are scraping slowly at the surface of her palms, a nervous rhythm Fitz remembers from the times their parents fought or when she had to go to the doctor's or if her dad was late coming home. He hates that he's the one who's caused it, the familiar nervous tic he knows makes her palms as red as the rings around her eyes when she's crying, and he hates that things are weird and he can't reach out and still her twitching fingers with his steady ones and sooth her irritated palms. Since he cannot use his hands to keep hers from scratching, he settles into his own nervous habit, plucking at the sleeves of his jumper, feeling the cloth fray under his blunt nails and callouses. Simmons wants to swat his hands away and tuck them into his lap and trim away the stray threads on his sleeves, fix everything up like she always does, but she can't seem to breathe or speak, let alone move to do anything as personal as that. 

"So." Fitz says, clearing his throat awkwardly as he moves to sit on the bed and thinks better of it, then moves to the floor, his long legs locking around each other clumsily as he tries to fold himself up in front of Simmons. 

"Er, yes. So." Simmons manages to stammer, staring intently at the toes of her favorite red converse. Fitz is only a few feet away from her, she could reach out to smooth his hair and fix his collar with ease, just like she always used to, but it feels like there's a thousand miles or an ocean between them, and the ocean is made of the fear churning in her heart that if she reached out to him, for the first time in her life, he would flinch away. She would rather spend the rest of her life walking tenderly around the broken eggshells of their friendship, never again even toeing the line they walked their entire lives, than test the waters on the other side and watch the one person she's ever felt truly close to flinch away from even the lightest graze of fingers. Fitz looks at her for a few moments, and she can feel his eyes on her just like she always has, but she doesn't lift her eyes from her shoes. 

"This is bloody stupid, Jem. We're both damn geniuses, we've been friends for years, and here we are, can't even look each other in the damn eyes, stuttering like the just fuckin' met and have only a tenuous grasp on the english language, all because we happened to smash our lips together for like half of a second." his voice is gruff and tired and irritated and he knows immediately what he said sounds awful, and without even looking at her again, he can feel Simmons shrinking in on herself and he hangs his head in his hands. He's meant to know her better than that, be more careful with her than that, especially when she's nervous and it takes all he has not to smash his fist into the floor in frustration but he knows she hates it when he does that. 

"Oh, like it's all my fault?" she says suddenly, her voice two parts hurt and one part angry, all rawness and exhaustion. "I was perfectly fine before you kissed me! I had my private feelings I ignored and never talked about and I was perfectly content to do exactly that for the rest of my life! But then you had to be the one to go get all confusing and kiss me. So don't act like you aren't at least partially at fault here. I would have loved you quietly for the rest of my life and nothing would have ever changed between us and we wouldn't be bloody fighting right now." 

"I... You.. What?" Fitz blinked rapidly, directing his gaze up at her again. 

"Oh don't play dumb, you dolt. You knew, I know you knew. I could tell. Everyone and their third cousin knew. Maybe you didn't let yourself think you knew, but you knew, I could see it in the way you'd look at me when I fixed your collar or fussed over how much you were eating. But I kept my mouth shut because I care far more about keeping my best friend than I do anything else. As long as you ignored it, so could I." her voice is still rough and tired, edged with a bitterness that stings Fitz's brain as she continues talking, but not as badly as the way she crosses her arms and leans further away from him stings in his chest and he can almost swear he hears something in the room crack and break as the tone of her voice cuts him open.

"I was jut as fussy as you though. I braided your hair and made your tea and cleaned up your scraped knees even though I hated blood. If I should have known, you should have known too. Why didn't you ever SAY anything?" his voice has lost it's anger, instead it's just low and sad and confused. 

"Why didn't I say anything? Have you heard yourself, Mr. Cynic? Any time our parents fought, they were on the edge of a divorce. You talk constantly about how love, especially young love, was stupid and never lasted and you were too busy with your work for any of that 'nonsense' anyway. Or if you weren't talking about the inevitability of love ending or divorce rates, you were mooning over some older girl. I never had any reason to say anything. I was afraid if I did you'd run away like a startled deer and I'd be left to clean up the pieces of a life without you, something I think I forgot how to do at some point, as stupid and illogical as that makes me seem."

"S'not just you. I couldn't live without you anymore either. I mean, come on Jem. You've got to know I need you just as much as you need me. You pick my clothes for me, for god's sake. You pick my clothes and make sure I eat and fix my collars and you... you take care of me. And I take care of you. That's just... that's what we do. So we've got to... we've got to figure this out, fix... whatever this is, and get back to normal. Or, maybe not normal but... better than we are now?"

She doesn't say anything to him, but she pats the mattress next to her and nods her head slightly. So Fitz stands and sits next to her, not as close as he normally would, but it still feels more normal that sitting on the floor, away from her. She reaches her hand out and angles one finger towards him. 

"Pinkie promise we'll always be best friends. No matter what." she still won't look at him, but her voice is soft and even and no longer sounds like a knife slicing haphazardly through the space between them. He links his smallest finger with hers and squeezes, nodding.

"Always, Jem. Always."

Gently, she slips her pinkie past his and one by own moves her fingers down until her hand is underneath his, turning her fingers up to wind into his. He wraps his around hers into return, and she can feel the thrum of his pulse against her own wrist, and the rhythm is slow familiar she thinks she could recall it in her sleep. She tilted her head then finally, auburn waves shifting away from her face as she looked at Fitz for real for the first time since he walked into the room. She wants to lean into him, aches to find out what his lips feel like of her own volition, knowing he wants it the same way she does. But fear is still coiled into her chest. squeezing her heart and making her afraid to move. But Fitz can see what she's thinking, just like always, and even as his pulse jumps, still pounding in time with her own, and his hands shake, he slowly closes the distance between them, until the feeling in her chest loosens enough to make this infinitely massive and infinitely minuscule leap from occupying her spaces to occupying his. And when his lips brush hers, her eyes shut of their own accord, and if she didn't know better she would have thought that the entire world simply stopped spinning on its axis, halting all of time and space to let this moment unravel itself slowly and wrap itself around them, tying their hearts together with a knot that would never be undone. Eventually they pulled away, their hands still clasped tightly together, both flushed as dark as the sheets on Simmons' bed. 

"So that's why people like kissing so much, then. I get it now." Fitz mumbles, his voice tinged with embarrassment. Simmons actually giggles a little and the sound sends a wave of calm through Fitz. If Simmons could kiss him and laugh at his jokes, then everything would probably be okay. He turns on the bed, letting go of her hand to sit crosslegged next to her, and as if she already knew, she does the same, knocking her knees against his. And just like that, everything is fine again. It's so simple, second nature, for them to occupy the same space. It always was. Simmons rests her forehead against his and smiles, Fitz's favorite smile, the one she sends his way when he's gotten her a particularly good present, or when he brings her tea in the morning before she even asks for it, and he thinks maybe his heart forgot to beat for a moment. 

"We should tell our parents. I dunno about my dad, but I don't think your mum will be surprised. I think she knew I had feelings for you." 

"Are you sure we should just.. tell them? Won't they think it's weird? What if they tell us to break up?"

"I don't think they will. At least I doubt my dad would, and your mum hardly seems like the type either." 

Fitz bites his tongue to keep from asking the question he so desperately wants to ask. But Simmons can read it in the stiffness of his fingers and the stretch of his neck, can see the 'but what if we break up' written in his eyes as plainly as if he'd spoken it, so she squeezes his hands hard enough to make sure he reads her thoughts right back. 'We won't'. And because she's Simmons, he believes her. 

They tell their parents the next day over Skype, and they are both balls of tight and nervous energy, clutching hands under the table so hard it hurts. But Simmons was right, her father doesn't mind and his mother figured it out ages ago. No one at school is surprised, and no one really says anything, save for a few cracks from the guys about Fitz's penchant for girls with dark hair suddenly making a lot more sense. Mostly, nothing changes. Fitz still braids her hair in the mornings, and she still ties his ties and steals all his jumpers when its cold. They still have movie marathons and study together and draw in each other's notebooks, and at the end of the day, the only difference is that those little moments of remembering they should pull away, stop touching, fade away, slowly replaced by other things to know and remember. Simmons' knees are ticklish, and Fitz sneezes if she scratches behind his ears. it isn't always easy, they've always bickered, and they are too similar and too different at the same time, but it works itself out because it's in all the right ways. When all is said and done, they would make it through anything, because nothing ever matters quite as much as the other, or the way their heartbeats always seem to be in sync, one giving as the other takes.

**Notes for the Chapter:**

> And it's done! This silly, self-indulgent fic is over! I hope a few of you enjoyed reading this as much as I did writing it!


End file.
